Means for transporting concrete



Oct .20, 1931. C. G. A..SCHM|DT, JR 1,828,343

MEANS FOR TRANSPORTING CONCRETE Filed Dec. 11, 1928 3 Sheets-Sheetl llllllll-l 1931- c. G. A. SCHMIDT, JR 1,823,343

MEANS FOR TRANSPORTING CONC RETE Filed Dec. 11, 1928 s Sheets-Sheet 2 MCW ffOP/VEYJ.

Oct. 20, 1931.

C. G. A. SCHMIDT, JR

MEANS FOR TRANSPORTING CONCRETE Filed Dec. 11, 1928 3 Sheets-Sheet 3 477'0/P/VEV-5.

Patented Oct. 20, 1931 UNITED STATES A ENT oFFiC oAN ROAD MACHINERY COMPANY, INo.,' o KENNETT SQUARE, PENNSYLVANIA, A coRroRA'rIoN or DELAWARN A f "ivrnANs non raANsroRmNG- coNcnErE Application filed December 11, 1928. Serial No. 325,314.

porting concrete and more particularly to a vehicle .body which is adapted to mixer maintain mixed a charge of wet concrete during transportation. 7 a

I-Ieretofore it has been attempted to mix concrete at central mixing plants and transport the concrete from such plants to the place of use. At first, ordinary dump trucks were used but it was found that in a very short time after loading, and probably due to vibration of the truck during transportation, the stone, being heavier than the more liquid portions of the mix, would settle on the bottom of the truck body, forming a hard compact mass which was removable only with difficulty, resulting in many rejections of the concrete and consequent losses.

To avoid these difficulties, various truck i do bodies have been designed of the rotary type or having blades therein. In one form of this construction, the revolving tankis provided with a plurality of inwardly extending blades which are designed to churn the concrete, thus effectively maintaining a proper mixture.

Such construction has been found impractical, however, because, due to improper de sign, the concrete collects and solidifies at the junctions of the blades with the walls of the cylinder, coating them and rendering them substantially ineffective and preventing the ready removal of the mixed concrete.

To avoid this objectionable feature resulting from the use of blades, attempts have also been made to use smooth walled cylindrical tanks concentric with the axis of ro tation. In such tanks, although some mixing occurs, the tanks are only efiective to a relatively slight degree to maintain mixed 49 an already thoroughly mixed concrete. They are inoperative to actually mix the unmixed ingredients to form a finished concrete. Consequently, the use of such tanks necessitates complete mixing prior to the filling of the tank, a process more costly than that resulting whentanks with properly designed blades are used, since then the unmixed ingredients may be dumped into the tank and thorough mixing will take place during transportation.

50 A further objection to the use of such the walls ofthe tank.

proved method of handling and manipulatsmooth walled tanks of circ'ularcross section is the necessity of having thetank substantially more than half. full in order to even maintain mixed an already mixed'conc'rete.

It is found that if the tank islesslthan half full substantially no mixing will occur, Furthermore, in these smooth walled tanks, in order to obtain any mixing a more vigorous rotation is necessary, the result ofiwhich'is rapid wearing ofthe walls of the tank. If blades are used, a more thorough mixing takes place with less vigorous rotation and the blades, which are relatively cheap andfm a y be replaced, take up thefwea'r rather than The broad object of the present invention is, accordingly, the provision of a rotary tank of the character described which avoids the objections noted above to both smoothwalled cylindrical tanks concentricwith the. axis of 7 rotation and those provided with blades in the usual manner, and which will accomplish both mixing and maintenance of mixing in an effective manner Without, undue wear on i the tank. A further object is theprovision ofineans for imparting axial movement'to the ingredients or mixture during rotation of the tank.

Another object is the provisionof'animso ing a concrete mixture to prevent segregation. a A

A still further obj ect relates to an improved arrangement for discharge to preventuncontrollable gushing of the concrete from the tank and thereby to permit the efiicient use of chutes.

These and other more specific objects of the invention and their accomplishment will be apparent from the followingdescription read in conjunction with the accompanying drawings, in which:

-'Fig. 1 is a-diagram'matic elevation show- 5 ing one modification of the improved transporting and mixing means;

Fig. 2 is a section of the tankon line 2-2 ofFigl; j V r Fig. 3 is an elevation of a modified form of tank;

Fig. 4: is a vertical section on line 4.-et of Fig. 3;

Fig. 5 is a diagrammatic side elevation of a further modified form of tank embodying the principles of the invention;

Fig. 6 is a rear elevation of the tank shown in Fig. 5;

Figs. 7 and 8 are diagrams illustrating the actions of the tanks shown in Figs. 1 and 5. respectively.

Referring first to 1 and 2, the chassis 2 of a motor truck has pivotally mounted thereon about a transverse horizontal axis at its rear a supporting frame 4 on which is mounted the rotary tank 6 and its driving motor 8. The driving connections, lifting means for the supporting frame for discharge, etc, may be of any ordinary type and consequently are not described in detail. Instead of being driven by a'separate m otor, the tank could, of course. be driven by the truck motor, or, if mounted on a trailer or railroad car. be driven by the wheels thereof during movement.

The tank Got this modification comprises polygonal end walls and rectangular side walls connecting the corresponding sides of the polygonal end walls. While in the present instance the end walls are hexagonal, 1t will be obvious that they may be of other forms and need not be symmetrical polygons. The meeting edges of the side walls are preferably rounded, thus producing a smoother action and less wear. A charging opening provided with a removable cover 13 is pro- Vided in one of the side Walls, while a discharging opening 14: provided with a suitable gate is formed in the rear end wall. Although this latter opening is shown as at one of the sides of the polygonal end wall, it may be advantageously placed at a vertex as will bebrought out below in connection with a-further modification.

Before proceeding with. a description of the modification shown in Figs. 3 and 4c, the action of the modification described will be discussed, since it embodies the common features of action of both modifications. Referrin-g to Fig. 2, a charge of concrete (or partially mixed constituents) is lndicated at 16, the tank being assumed to rotate in a clockwise direction as viewed therein. During suchrotation, each of the side walls of the tank acts as a blade serving to thrust the mixture or create a space into which it will flow as indicated by the vectors, this action being due to its constant change of angularity to the horizontal. Thus, besides the production of local circulation adjacent the walls, the mass as a whole is circulated, being folded over on itself or kneaded as indicated at 18 and thence flowing to the position 20 from which the mixture is forced downwardlyas indicated by the vector.

The action described is substantially independent of the amount of the plastic mass in the tank since the kneading action is primarily due to the changing angularity of the sides and not to friction of the mass with the walls such as produces a circulation of a mixture in a circular cylindrical tank and necessitates its being substantially more than half full. By reason of the provision of the sides which act as blades, the mixing is to such an extent positive and thorough that it is possible to mix duringshort transportation the ingredients which may be placed therein in unmixed condition. Mixing of unmixed ingredients by the frictional action in a circular c riinder without blades and concentric with the axis of rotation is entirely impractical.

Referring now to Figs. 3 and 4, the tank therein shown consists of polygonal heads 22 and 24 displaced relatively to each other about a common axis through an angle equal to half that subtended by one side. In the present instance, the heads being hexagonal, the angle of displacement is 30.

The side walls 26 of this tank are triangular, each wall having a base on a side of one end and a vertex at the opposite vertex of the other end. The junctions of the side walls are preferably rounded as described in connection with the previous modification. This tank is illustrated as driven through a ring gear 28 carried thereby and driven by a pinion from a motor in the usual manner, although it will be understood that it may be driven in the same manner as the modification already described.

In this form of tank, the discharge opening is preferably provided at one of the vertices of the rear head, being normally covered by a gate 30. The bottom edges of the opening then coincide with the sides of the head adjacent the vertex and the opening is in line with the trough formed, as shown in Fig. 4, by the wall 26 having its vertex at the said vertex and walls 26 and 26 having their bases at the adjacent sides of the head.

When the discharging opening is at the lowermost position as illustrated in the figures, the bottom of the trough formed by wall 26 will slope downwardly and rearwardly. The effect of this upon the discharge when the tank is horizontal (as it is maintained until the major portion of the contents are removed) is to give the lower portions of the mass a movement towards the discharge together with the upper portions which would flow due to the removal of the restraining wall formed by gate 30. As a consequence a stream, all portions of which have about the same velocity, will flow outwardly through the opening in a smooth manner permitting. the use of chutes to conduct it to the point desired. It, as in the usual form of tank, the bottom is horizontal, no such movement of the lower stratum of the mass occurs and the more rapid movements of the overlying strata produce gushing which will cause the mass to overflow thesides of a chute.

The above improveddischarge is: effected whether blades or fins'are used or not. If blades are considered desirable, however, a pairof these, indicated at 32, may be arranged to flank the sides of the discharge opening and preferably tofollow to a greater 'or less degree the sides of wall 26. These blades, which are desirablylofthe type disclosed in the applicationof Earle S. Philips,

Serial, No. 305,338, filed September 12, 1928, serve to further control the flow as described in that application. An additional pair of blades 34 are illustrated asarranged opposite blades 32 although it will be understood that blades may be omitted altogether or placed otherwise than as illustrated. A charging opening is provided as at 36.

Assuming first that the tank is without blades, it will produce during its rotation an action similar to that described above in connection with the first modification. In addithe tank due to two causes. The first of these causes is the sloping junctions between the sides 26, which, by reason of the difference in angularities of the portions of the sides contacting with parts of the mass in longitudinal alignment, produce combined rotary and longitudinal movements in the mass, the longitudinal movement being reversed during an angular movement equal to half the angle subtended by a side of a head. The second cause of longitudinal motion results from the alternate forward and rearward slopes of the lowermost sides during rotation. Assuming a clockwise direction of movement in Fig. 4, for example, a movement of will produce a change in slope of the lowermost portion of the tank from the downward and rearward slope of side 26' to the downward and forward slope of side 26. The result of the combined actions referred to is the production of thorough mixing of the mass which is found particularly effective in producing a homogeneous mixture from unmixed ingredients.

If blades or fins are used as illustrated, there is, in addition to the actionsdescribed above, a further mixing action by the blades of the type described in the application of Philips referred to above. These blades are spaced from the walls to prevent their fouling by hardened concrete, the spacing preferably increasing towards the front of the tank. Due to their angular positions relative to the axis of rotation they also impart longitudinal movements to the mass. As a result of the interaction of the various members imparting motions to portions of the mass, a most thorough kneading is obtained.

is necessary to erect at a central plant onlyE means for measuring proper batches of ingredients for delivery to the tank, without the necessity of providing any mixing means the plant, since thorough mixing will take place during the first few minutes of trans-( portation, the tank acting, thereafter, to maintain the ingredients thoroughly mixed. While without blades, the use of a polygona-l tank permits much less rapid rotation for I satisfactory action than a circular cylinderfithe use of blades further decreases the necessary speed so that erosion of the tank may be minimized, the erosion being due to frictional movement rather than to the positive 3 pushing movement imparted by the plane walls, and the relative surface movement producing the friction being minimized at low speeds. tlon to this act1on, however, 1t will also serve to impart axlal movement to the contents of The improved method of handling concrete mixtures, tllElbfiSlC- prlnclples underlying the construct on of tanks for carrymg out "the method, and the scope-of the invention may be best brought out by considering the tank illustrated in Figs. 5 and 6. l/Vhile this tank is not considered a desirable form because cf practical difficulties in construction, its very considerable divergence from the constructions heretofore described serves to emphasize the basic features of the invention which are embodied therein.

The axis of rotation of this last form of tank is designatedC-G. The ends 38 and 4&0 lie in planes perpendicular to the axis CG and are circular and eccentric with respect to that axis, their respective centers being indicated in Fig. 6 at 38 and 40" at opposite sides of the axis. The side walls 42 of the tank consist of a cylindrical surface of straight line elements'joining the circular ends. In this way a tank is produced all of @110 the radial cross-sections of which, withthe exception of the one midway between the ends (assuming their equal eccentricity), are eccentric circles. The discharge opening at is located at the most eccentric portion of the 5M5 periphery of the rear end 40.

Considering the action of the tank with respect to material in a radial plane, the. simi larity of action of the modificaticns inFigs. 20 2 and ,5 will be clear from an examination of Figs; 7 and 8, respectively. During a rotation of the tank of Fig. 2 through a wall of the tank moves from position a of Fig. 7 through position b to position cl Dur- C1325 take place in the operation of the tank of Fig. 3.

In the case of the tank of Fig. 6, during a half revolution the wall occupies successive- 1y positions m, n and with similar changes of angularity and positions relative to the center. a similar effect will be obtained if a tank of elliptical or other non-circular cross-section is used.

lVith respect to longitudinal action, the ellects of the modifications of Figs. 8 and are also similar. In both cases the intersection of a vertical axial plane with the tank wall below the axis slopes downwardly alternately towarcs the front and rear of the tank, resulting in reversal of flow taking place in the first tank every and in the second tank every 180. The discharge position of the latter tank is that shown in Fig.

'6 when a sloping trough, similar in effect to that described in connection with Fig. 3, is formed.

Summarizing the above, the improved method of handling the mixture will be seen to consist of the following two simultaneously performed operations:

(1) a combined traversing and kneading action resulting from the change in angularity of a contacting surface together with a traversing movement of the surface; and

(2) an oscillatory movement imparted to the mass periodically by change in slope of the bottom of the tank.

Besides these actions, there is imparted by the blades disclosed, if these are used, an internal churning action.

Each of these actions is most advantageous in effecting mixing and preventing segregation of the constituents and the combination of these various actions insures more rapid and thorough accomplishment and maintenance of uniformity. The tank of Fig. 5 is inferior to the polygonal type in that the period of repetition of the actions is longer.

A tank serving to accomplish the operation designated (1) above need only have a radial cross-section which is other than a circle concentric with the axis of rotation. Accordingly, it is not desired to limit the claims to any particular type of cross-section since polygonal, oval or eccentric circular cross-sections will serve to perform this operation.

What I claim and desire to protect by Let- V ters Patent is:

1. Means for transporting concrete comprising a motor driven vehicle, a rotary tank mounted on the vehicle and having end walls and an outer wall, one end wall being provided with a discharge opening adjacent its edge, portions of the outer wall forming a trough sloping downwardly towards the discharge opening when the opening is below the axis of rotation and the axis is horizontal, and means for rotating the tank.

2. Means for transporting concrete comprising a motor driven vehicle, a rotary tank mounted on the vehicle and having end walls and an outer wall, one end wall being provided with a discharge opening adjacent its edge, portions of the outer wall forming a trough sloping downwardly towards the discharge opening when the opening is below the axis of rotation and the axis is horizontal, blades within the tank and extending longitudinally thereof adjacent the opening, and means for rotating the tank.

In testimony of which invention, I have hereunto set my hand, at Kennett Square, Pa, on this eighth day of Dec, 1928.

CARL G. A. SCHMIDT, JR. 

